Geoff Power

Environmental impacts of hydroelectric projects on fish resources in China

China has embarked on a programme to vastly expand its hydroelectric generating capacity and this is certain to alter its freshwater and anadromous fish communities. To provide some insight into the direction and consequences of the likely changes, four (>250 000 kW) existing facilities were selected for review. The Gezhouba Dam, on the Changjiang River, commissioned in 1981, is a low-head run of the river facility. The Xinanjiang Dam (1959) is a high-head dam and the Fuchunjiang Dam (1968) is a low-head, run of the river dam, both sited on the Quiantang River. The Danjiangkou Dam (1968) is a high-head dam in the Han River, a tributary of the Changjiang River. Impacts on fish were classified as those caused directly by the structures, those resulting from changes in physical and chemical factors in their environment and those induced through biotic changes in their habitat. Migrations of anadromous and semi-migratory fish were blocked by the Gezhouba Dam, although some species adapted to the new environment by reproducing downstream. Below the Xinanjiang and Danjiangkou dams spawning was delayed 20–60 days by lower water temperatures. Reduced water velocities and less variable discharges caused spawning grounds below the dams to be abandoned. Marked changes in the hydrological regime caused the extinction of Macrura reevesii, a highly valued fish, in the Qiantang River. The fish communities in the Qiantang estuary were affected by the regulated discharge. Freshwater species fell from 96 to 85, whereas marine species increased from 15 to 80. Loss of habitat eliminated torrential habitat species from the areas inundated by Xinanjiang and Danjiangkou Reservoirs; lentic fish replaced lotic species and now dominate the reservoir fish communities. The expanded aquatic habitat was beneficial for fishery production. Catches from the two reservoirs continue to increase 20 years after impoundment, but are supported by extensive artificial propagation and stocking. There is no doubt that, when the expansion of Chinas hydroelectric facility network is complete, the fish communities in its rivers will be markedly changed.

Seasonal migrations and reproductive patterns in the lake sturgeon, Acipenser fulvescens, in the vicinity of hydroelectric stations in northern Ontario

This study was conducted in order to evaluate seasonal migratory behaviour and reproductive pattern of lake sturgeon in a confined region of the Mattagami River system in northern Ontario where river flow is regulated by hydroelectric works. Radio tracking and the systematic sampling of lake sturgeon using gill nets indicated that the distribution of fish throughout the study site varied on a seasonal basis. This distribution was related to the migration of individuals to potential spawning sites in the spring, a post-spawning dispersal to feeding areas and late summer migration to an area of concentration on the Groundhog River which is a tributary of the Mattagami River. There was a high proportion of fish (about 50%), within the size range of reproductively active fish, found in the vicinity of suitable spawning habitat during early May. Measurement of the gonadosomatic index (GSI) and plasma sex steroid hormone levels revealed a divergent pattern of reproductive development between the sexes. Female sturgeon exhibited a prolonged period of ovarian regression following spawning. Resumption of ovarian development was not evident until September and was characterized by an increased GSI and plasma levels of testosterone and 17β-estradiol. In contrast, male lake sturgeon began testicular recrudescence within one month of spawning with the GSI reaching prespawning levels by September; reproductive hormones were at prespawning levels by the end of June. It seems that hydroelectric works has complex effects on sturgeon in the Mattagami system. The extensive migratory behaviour of lake sturgeon within the study area make it prone to impingement or entrainment whereas the altered river flow appears to enhance reproductive development.

Evaluation of Atlantic salmon parr responses to habitat improvement structures in an experimental channel in Newfoundland, Canada

Distributional patterns and microhabitat selection of Atlantic salmon (Salmo salar) parr were investigated in relation to habitat improvement structures in a controlled flow experiment channel at Noel Pauls Brook, Newfoundland. The channel consisted of six replicates, each containing three randomly arranged treatments. Each replicate included a control treatment with no habitat modification, a mid-channel treatment with a boulder cluster and low-head barrier dam, and a stream bank treatment with undercut banks and wing deflectors. The influence of size class, density, discharge and diurnal/nocturnal differences on microhabitat selection were evaluated. Results showed that the mid-channel treatment did not serve its purpose at lower discharges (0.032–0.063 m3 s−1), and as a result was not the treatment of choice. However, as the discharge increased (0.13 m3 s−1), more salmon took up residence in this treatment. In all experiments, greater depths were selected in the stream bank treatment, and salmon parr in the mid-channel treatment consistently selected positions closer to cover. Larger parr preferred greater depths and were found closer to the improvement structures. Benthic and drifting food availability were also estimated, and results showed that ‘funnelling effects’ of the drift were created near the structures. This study indicates that these structures have the potential to create favourable feeding sites, and provide the necessary physical characteristics required by salmon parr.

Catch Records — Facts Or Myths?

The ideal barometer of Atlantic salmon management success would be complete and accurate records of how many, where and what sizes of salmon were caught in the past, the types of gear used and the effort expended. While such records would prove most helpful, they still would not be easy to interpret due to varying response times to management decisions, and the confounding effects of climate and other environmental influences on salmon stock density and behaviour. The scarcity of good records and the difficulty of interpreting them provides a real challenge, stimulating both the historian and the detective in us to sort myth from reality, trying to provide a reliable background against which present day results can be judged.

Age at maturity in landlocked and anadromous Atlantic salmon parr from two Québec rivers

SynopsisAge at maturity in male Atlantic salmon parr from landlocked populations in the Watshishou and Musquaro Rivers is significantly greater than in anadromous populations from the same rivers. We conclude that high post-smolt mortality in anadromous stocks is conducive to male parr maturity at an early age. We also suggest that the lower proportion of maturing male parr in landlocked stocks may be related to competition among males for mates and the smaller ultimate size of spawning adult landlocked salmon.